1. Field of the Invention
The present invention relates to photographic film processing equipment. In particular, the present invention is a photographic film type sensor system for determining the type of film entering a photographic cine processor.
2. Description of the Prior Art
In the photofinishing industry, cine processor machines are used to continuously develop long webs of photographic film. Typically, several different sizes or formats of photographic film may be processed by the same cine processor. For example, in certain processors 110, 126 and 135 format film are processed. Other processors are capable of processing these three film formats as well as 46 mm, 120/220 and 70 mm format films.
In the prior art, cine processors typically have used flowmeters to control chemical replenishment of processor fluids. An operator has been required to manually adjust these flowmeters each time a new film type or film leader enters the cine processor. In general, therefore, the users of cine processors have been very dependent upon the skill of their operators for making accurate replenishment adjustments and, more importantly, for remembering to make the adjustments each time a new film type or film leader enters the processor.
As the processes and chemicals used to develop photographic film have continually been improved, the chemicals used for replenishment have become more concentrated. As a result, the margin for error in replenishment has decreased. Automatic replenishment of processor fluids in cine processors has become, therefore, very attractive.
In order to properly control replenishment in a cine processor on an automatic basis, an automatic replenishment control system requires information as to whether leader or photographic film is entering the processor, and (if film is entering) the particular film type or format. If leader is being run through the cine processor, replenishment is not required. In the case of the various film types, each requires a different replenishment rate.
U.S. Pat. No. 4,222,657 by Leuchter describes a cine processor having a set of pneumatic sensors which sense and identify 110, 126 and 135 film formats. The pneumatic sensors are in the form of air nozzles arranged on one side of the film web, and a corresponding set of pressure air-operated switches on the other side of the web opposite the respective air nozzles. The pneumatic sensors identify the 110, 126 and 135 format films by sensing the perforations which are unique to these different film types.
The Model 1635 Kodacolor Continuous Film Processor by Eastman Kodak Company featured a film size detector which sensed both film width and format. The film size detector formed part of a system which controlled positive displacement replenishment pumps so that the proper amount of replenisher was supplied for the film size being processed. The Model 1635 processor accepted only 110, 126 and 135 film formats. The film size detector was a transmissive infrared detector having light-emitting diodes on one side of the film and corresponding infrared sensors on the opposite side of the film.
Another film type sensor which has been available in the prior art is the Photomatic Film Type Sensor, which has a U-shaped bracket which guides the film between three infrared sources and three infrared sensors. This film type sensor is also limited to 110, 126 and 135 film formats, and utilizes transmissive IR sensing to identify these three film types and film leader.
There is a continuing need for improved photographic film type sensors which are accurate, simple in construction, and which are capable of sensing a wide variety of different film formats, including not only 110, 126 and 135 film formats, but also 46 mm, 120/220 and 70 mm film formats.